Regulatable coolant pump having integrated pressure chamber

ABSTRACT

A regulatable coolant pump of an internal combustion engine having a pump housing in which a pump shaft with an associated impeller is rotatably mounted. The impeller conveys a coolant via an intake connection into a pressure channel of the coolant pump, a volume flow of the coolant pump being adjustable by a guide plate that externally surrounds the impeller at least in some regions and is displaceable by a pressure medium. The guide plate is connected in rotationally fixed fashion to the impeller and is continuously axially displaceable between two end positions and guided with a cylindrical bushing, with play at both sides, in an annular groove of the impeller or of an insert enclosed by the impeller. The guide plate, the pump shaft, the insert part, and/or the impeller together delimit a pressure chamber that is charged by the pressure medium in order to displace the guide plate.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of German Patent application No. 102011083805.8, filed Sep. 30, 2011, which is incorporated herein by reference as if fully set forth.

BACKGROUND

The present invention relates to a regulatable coolant pump of an internal combustion engine having a pump housing in which a pump shaft with associated impeller is rotatably mounted. The impeller conveys a coolant via an intake connection into a pressure channel of the coolant pump, a volume flow of the coolant pump being capable of being influenced by a guide plate. For this purpose, the guide plate externally surrounds the impeller at least in some regions, and can be displaced hydraulically in rotationally fixed fashion between two end positions by a pressure medium.

Vehicles are predominantly driven by water-cooled internal combustion engines. Through the use of a coolant pump, coolant medium is pumped in a closed circuit through coolant channels of the crankcase and of the cylinder head of the internal combustion engine, and the heated coolant medium is subsequently cooled back down in an air-water heat exchanger. To support the circulation of the coolant, a coolant pump is used, in particular driven directly by a belt drive. Due to an immediate coupling between the coolant pump and the crankshaft, the pump rotational speed is a function of the rotational speed of the internal combustion engine. It follows from this that, during a cold start of the internal combustion engine, the coolant circulates, delaying a desired rapid warming up of the internal combustion engine. In order to optimize the operation of internal combustion engines, it is necessary to reach the operating temperature as quickly as possible after a cold start. This reduces frictional losses and fuel consumption, and at the same time reduces emissions values. In order to achieve this effect, regulatable coolant pumps are used which have a conveyed volume flow that can be adapted to the cooling requirement of the internal combustion engine. After a cold start, first a zero conveying of the coolant pump is sought, and subsequently the volume flow for the cooling of the internal combustion engine continuously increases as a function of the temperature level that arises. In series of trials for optimizing the fuel consumption of internal combustion engines, rigorously applied measures for thermal management, inter alia in connection with regulated coolant pumps, succeeded in achieving a reduction in fuel consumption of ≧3%.

From DE 199 01 123 A1, a regulated coolant pump is known in which an external overlapping sliding element is allocated to the impeller as a measure for influencing the volume flow. The effective vane width of the impeller can be modified by the sliding element, which can be continuously axially adjusted by rotating a threaded guide.

DE 10 2008 046 424 A1 discloses a regulatable coolant pump for a coolant circuit of an internal combustion engine, driven by a traction mechanism drive. In order to influence a conveyed quantity, an axially displaceable guide disk is allocated to the impeller, said disc being axially displaceable by a push rod, placed inside the hollow shaft of the impeller, in connection with an actuator. The actuator comprises an anchor fixedly connected to the pushrod, said anchor being axially displaceable in a targeted manner via a proportional magnet. For this purpose, the electrically actuated actuator is situated before the belt pulley at the end face, and influences the axial constructive length of the coolant pump.

The regulated coolant pump according to DE 10 2005 062 200 A1 has a driven shaft, mounted in the pump housing, having an associated impeller and a valve slide that can be displaced pneumatically or hydraulically and that variably covers an outflow region of the impeller. On the valve slide there are situated a plurality of piston rods distributed about the circumference that run parallel to the pump shaft in the pump housing and that are guided in annular grooves or bores and are sealed in the pump housing by rod seals. The piston rods stand in operative connection at the annular groove with an annular piston placed in a pressure chamber. A displacement of the annular piston, acted on by pressure springs, and of the valve slide connected thereto takes place via charging of the pressure chamber with pressure, which has a pressure connection bore for this purpose.

SUMMARY

The object of the present invention is to realize a simplified and component-optimized hydraulic displacement of the guide plate inside a regulatable coolant pump.

This object is achieved in connection with various aspects and advantageous developments of the invention as described below and in the claims.

The present invention is based on the general idea that the pressure medium acts immediately on the guide plate in order to displace it hydraulically. For this purpose, the guide plate, together with an end face of the pump shaft and the impeller, delimits a pressure chamber. Alternatively, the pressure chamber determined by the pump shaft and the impeller can include an insert, fashioned as an intermediate element pressed onto the end of the pump shaft and surrounded externally by the impeller. With a bushing fashioned as a circular cylinder sleeve, the guide plate engages with a positive fit in an annular groove, open at one side, of the insert or of the impeller. In order to avoid a loss of pressure and/or loss of pressure medium, the bushing is set in the annular groove in sealed fashion. A preferred construction of the guide plate provides the use of an insert having a relatively large diameter, such that, due to the geometric dependence, a large pressure surface is created for actuating the guide plate. For the purpose of unhindered actuating movement of the guide plate, a depth of the annular groove exceeds the length of the bushing. In comparison with known solutions, the present invention has the advantage that using simple means, small constructive size, a reduced number of components, and greater operational reliability, not only a reduction of the volume flow but also a desired zero conveying by the coolant pump can be achieved in the closed state of the guide plate. The constructive outlay for realizing the measure according to the present invention is advantageously low, because special measures are realized neither at the pump drive nor at the pump housing. In addition, there results a cost advantage due to simplified assembly of the guide plate.

According to one preferred embodiment of the present invention, the impeller has an insert having a one-part or multi-part construction. For the rotational fixing, one end of the pump shaft is preferably pressed with a non-positive fit into a central receptacle or bore of the insert. The insert, performing the function of an intermediate element, can be made of various materials, preferably of plastic, metal, or a steel material. The impeller is preferably connected with a material fit, for example by a plastic coating, to the insert, acting as an insert. Alternatively, it is possible to press the insert into the impeller.

In addition, for sealing the pressure chamber and guiding the guide plate, a sealing element is provided that is positioned in stationary fashion in the annular groove of the stationary insert or of the impeller, said sealing element being supported in sealing fashion on the inside on the bushing of the guide plate. As a sealing element, an 0-ring or a sealing element made of a highly elastic and wear-resistant plastic is suitable, whose sealing lip is held on the bushing with a non-positive fit. The elastic sealing element advantageously compensates tolerances due to manufacturing or due to thermal expansion of the components abutting one another. Alternatively to a one-part construction, a reinforced sealing element is suitable in which the reinforcement is for example pressed into the annular groove and the sealing material is vulcanized on. The sealing element is preferably made completely or partially of a thermoplastic material, preferably polyvinylidene fluoride (PVDF) or polytetrafluoroethylene (PTFE). PTFE is suitable as a material due to its low coefficient of friction, good resistance to wear, and high resistance to the water-glycol mixture used in the coolant.

The design according to the present invention also provides that, for the axial displacement of the guide plate, the pressure medium flows into the pressure chamber via a longitudinal bore inside the pump shaft. For example, the pressure medium coming from a pressure medium source, guided via a control or regulating unit, can act immediately on the guide plate.

As a measure for avoiding an impermissibly high pressure level inside the pressure chamber, or for reducing the pressure, at least one radial passage is made in the bushing. For this purpose, a position of the opening is provided that, in an end position of the guide plate corresponding to the zero conveying of the coolant pump, enables a flowing off of a partial quantity of the coolant from the pressure chamber into a pressureless region or into an intake zone of the coolant pump.

In addition, with an outer rim oriented at a right angle the guide plate according to the present invention surrounds, with play, an outer contour of a rear wall of the impeller. The sealing of an annular gap that forms here is accomplished by a seal that is set in a radially oriented groove of the outer contour of the impeller rear wall, the seal lying against the rim of the guide plate at the inner side with a non-positive fit. This design supports the measure for realizing a zero conveying quantity of the coolant pump in an end position of the guide plate.

As a measure for ensuring the cooling of the internal combustion engine when there is failure of the actuator or of the pressure medium supply for displacing the guide plate, according to the present invention a failsafe device is provided. This is formed by a spring element situated in the annular groove of the insert that acts on the bushing of the guide plate, against the direction of force of the pressure medium. In case of damage, the spring element automatically shifts the guide plate into a position that corresponds to a maximum opening of the impeller and thus to the largest conveyed quantity of the coolant pump.

BRIEF DESCRIPTION OF THE DRAWINGS

Further features of the present invention result from the following description of the drawings, showing a preferred exemplary embodiment.

FIG. 1 shows a sectional view of a of a regulated coolant pump having a guide plate according to the present invention; and

FIG. 2 shows an enlarged view of a segment of the coolant pump according to FIG. 1, illustrating the design of the guide plate.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows a regulatable coolant pump 1 in longitudinal section, having a pump housing 2 in which a pump shaft 3 is rotatably mounted and having at an end side an impeller 4. An insert 5 is pressed onto a shaft stump of the pump shaft 3, said insert being externally surrounded by a rear wall 6 of the impeller 4. Curved vanes 7 of the impeller 4, which are shaped in the manner of a shovel and extend out from the rear wall 6, extend up to an end-face pump cover 8 whose opening cross-section defines an intake connection 9, via which the coolant enters axially into the coolant pump 1, and that exits radially into a pressure or spiral channel not shown in FIG. 1. A conveyed flow or volume flow of the coolant pump 1 can be influenced by an axially displaceable guide plate 10 with which an outflow region of the impeller 4 can be variably covered. The displacement of the guide plate 10 takes place hydraulically in connection with a displacing unit that can also be designated an actuating mechanism or actuator and that has a pressure medium source, a hydraulic pump, and a control or regulating unit. A control or regulating unit, for example electronically controlled, is preferably connected to an engine management unit of the internal combustion engine, whereby, as an immediate function of the coolant temperature or the operating temperature or taking into account further parameters, the respectively required coolant flow flows to the internal combustion engine via a corresponding setting of the guide plate 10. FIG. 1 is limited to the representation of a pressure medium supply 11 of the displacement unit, realized as a longitudinal bore inside the pump shaft 3 and leading up to a pressure chamber 12 limited by the guide plate 10 and by the pump shaft 3 and the insert 5.

For the continuous displacement of the guide plate 10 between two end positions defined by the pump cover 8 and the rear wall 6 of impeller 4, the pressure medium acts immediately on the guide plate 10. At the rear wall side, the guide plate 10 is connected in one piece to a cylindrically shaped bushing 13 oriented concentrically to a longitudinal axis of the coolant pump 1, said bushing being fitted with play into an annular groove 14. In order to seal the pressure chamber 12, a sealing element 15, positioned in a circumferential groove 16 of the insert 5, is supported on the inner side on a bushing 13, and prevents loss of pressure medium and thus loss of pressure. In FIG. 1, the guide plate 10 is supported on the rear wall 6, so that the largest opening of the impeller 4 results, in which position the coolant pump 1 conveys a maximum volume flow. Radially offset to the pressure chamber 12, the openings 21 are made in the guide plate 10 that are adapted corresponding to the profile of the vanes 7, said openings enabling an axial displacement of the guide plate 10 relative to the impeller 4. On the outer side, the guide plate 10 forms a rim 17 oriented at a right angle in the direction of the pump housing 2, surrounding an outer contour of the impeller rear wall 6 at a distance and thus having a length that exceeds the width of the rear wall 6. An annular gap 18 that results is sealed by a seal 19 that is set in a groove 20 of the rear wall 6 and lies on the rim 17 on the inner side.

FIG. 2 shows details of the impeller 4 and illustrates further details of the guide plate 10, in particular its shape and situation. A depth of the annular groove 14 inside the insert 5 is designed such that the actuating movements of the guide plate 10, and of the bushing 13 connected thereto, are not impaired. In order to avoid an impermissibly high increase of pressure inside the pressure chamber 12 when the guide plate 10 comes into contact with the pump cover 8, a partial quantity of hydraulic fluid can be diverted. For this purpose, a passage 22 for an exit of hydraulic fluid is made in an end region of the bushing 13. In the previously described end position of the guide plate 10, the passage is situated before the sealing element 15, so that an exit of hydraulic fluid results, together with a lowering of the pressure level inside the pressure chamber 12. Differing from the depiction shown in FIG. 2, the insert 5, pressed into a receptacle 27 of the rear wall 6 of the impeller 4, can also have a multi-part construction, in particular a two-part construction. For this purpose, a tubular inner part can be combined with an outer part that encloses the annular groove 14. In order to ensure the functioning of the coolant pump 1 when there is a failure of the actuator or of the pressure medium supply for actuating the guide plate 10, a failsafe device 23 is provided. For this purpose, a spring mechanism 26, in particular a pressure spring, is placed between an end-side collar 24 of the bushing 13 and a stop 25 of the insert 5 inside the annular groove 14, said spring applying force to the guide plate 10 in the direction of the rear wall 6, and thus opposite the flow of pressure medium. The failsafe device 23 has the effect that when there is a drop in pressure inside the pressure chamber 12, the guide plate 10 is automatically displaced in the direction of the arrow up to a stop on the rear wall 12, setting a maximum opening of the impeller 4.

LIST OF REFERENCE CHARACTERS

1 coolant pump

2 pump housing

3 pump shaft

4 impeller

5 insert

6 rear wall

7 vane

8 pump cover

9 intake connection

10 guide plate

11 pressure medium supply

12 pressure chamber

13 bushing

14 annular groove

15 sealing element

16 circumferential groove

17 rim

18 annular gap

19 seal

20 groove

21 opening

22 passage

23 failsafe device

24 collar

25 stop

26 spring mechanism

27 receptacle 

1. A regulatable coolant pump (1) of an internal combustion engine, comprising a pump housing (2) in which a pump shaft (3) with an associated impeller (4) is rotatably mounted, that conveys a coolant via an intake connection (9) into a pressure channel or spiral channel of the coolant pump (1), a volume flow of the coolant pump (1) being adjustable by a guide plate (10) that externally surrounds the impeller at least in some regions and that is hydraulically displaceable, the guide plate (10) is connected in rotationally fixed fashion to the impeller and is continuously displaceable axially between two end positions, the guide plate (10) is guided by a cylindrical bushing (13) extending therefrom, with play at both sides, in an annular groove (14) of the impeller (4) or of an insert (5) surrounded by the impeller (4), and the guide plate (10), the pump shaft (3), and the insert (5) together delimit a pressure chamber (12) that is charged with pressure medium in order to displace the guide plate (10).
 2. The coolant pump as recited in claim 1, wherein the pressure chamber is defined by the guide plate (10) together with the pump shaft (3), the insert (5), and the impeller (4), as a function of a position of the guide plate (10).
 3. The coolant pump as recited in claim 1, wherein the insert (5) has a one-part or multi-part construction and is made of plastic, metal, or a steel material, and is set into a receptacle (27) of the impeller (4) with at least one of a material fit or a non-positive fit.
 4. The coolant pump as recited in claim 1, wherein for the sealing of the pressure chamber (12), a sealing element (15) is provided that is positionally fixed in the annular groove (14) of the stationary insert (5) or of the impeller (4), said sealing element being supported on the inner side on the bushing (13) of the guide plate (10) with a non-positive fit.
 5. The coolant pump as recited in claim 1, wherein for the axial displacement of the guide plate (10) the pressure medium flows into the pressure chamber (12) via a pressure medium supply (11) provided as a longitudinal bore in the pump shaft (3).
 6. The coolant pump as recited in claim 1, wherein in an end position of the guide plate (10), a pressure level inside the pressure chamber (12) can be reduced via at least one radial passage (22) in the bushing (13).
 7. The coolant pump as recited in claim 1, wherein an external angled-off rim (17) of the guide plate (10) surrounds, with play, an outer contour of a rear wall (6) of the impeller (4), maintaining an annular gap (18).
 8. The coolant pump as recited in claim 7, wherein a seal (19) set in a radially oriented groove (20) of an outer contour of the impeller rear wall (6) is supported with a non-positive fit on the rim (17) of the guide plate (10).
 9. The coolant pump as recited in claim 1, wherein the bushing (13) of the guide plate (10) works together with a failsafe device (23) provided as a spring mechanism (26) and set in the annular groove (14) of the insert (5) or of the impeller (4) as a countermeasure against failure. 